You would like to work on Geodynamics ? Join us as a Ph.D. candidate !
Apply online here
Subjet
Controlling factors of the organization of carbonaceous materials during geological burial on naturally and experimentally strained rocks
Advisors
Romain Augier, Hugues Raimbourg, Mohammed Boussafir, Yan Chen (ISTO), Abdeltif Lahfid (BRGM) et Asuka Yamaguchi (University of Tokyo)
Abstract
Carbonaceous material are common components of the metasediments, mainly deriving from the diagenetic and then the metamorphic evolution of the organic matter initially present within the sediment. This progressive transformation through carbonization and graphitization drive to an increasing and irreversible organization of the carbonaceous materials toward well-crystallized graphite, the last step in the evolution. Consequently, the degree of organization of the carbonaceous material has been considered as a reliable indicator of the metamorphic conditions at peak-conditions (e.g. Rietmeijer & Mackinnon, 1985; Wada et al., 1996). More recently, the quantification of the degree of organisation of the carbonaceous material by Raman spectrometry has been proposed as a new geothermometer (RSCM geothermometer) for a wide range of temperature (200-650°C ; Beyssac et al., 2002 ; Rahl et al., 2006 ; Lahfid et al., 2010). This geothermometer is currently became a reliable tool in metamorphic petrology (e.g. Cottle et al., 2011 ; Scharf et al., 2013 ; Augier et al., 2015 ; Beaudoin et al., 2016). However, the fine understanding of the graphitization processes remains limited particularly concerning the loss of functional groups and the formation of a lattice of graphene. In addition, the effet of deformation is often proposed to explain differences, local anomalous temperatures in a first order temperature tendancy. This effect of the deformation on the organisation of carbonaceous material therefore remains porrlystudied exept in the case of fast movements responsible for frictional heat release. Recent studies performed pseudotachylites (Ito et al., 2016 ; Yamaguchi et al, in prep) have indeed shown a moderate increase of the organization of carbonaceous material. In this case, it is not possible to make clearly the difference between the effect of temperature and the potential effect of deformation. Besides, numerous questions remain currently unexplored such as the effects of localized deformation that do not produce partial melting (brecciation) or the effect on ductile deformation (mylonitization).
This PhD project explores the effects of both temperature and deformation on the organization of the carbonaceous material on naturally and experimentally strained rocks with a molecular/functional control. A dense sampling at different scales will be performed on the field, along strain gradients already recognized by the members of the supervising team (Japan, Spain ou Greece). Variations in the organization of carbonaceous material will be compared with estimates of the amount of strain. In parallel, experiments on a Paterson Press will be conducted with controlled temperature, duration and amount of simple shear deformation on natural shales whose carbonaceous content will be finely characterized from the textural, chemical and functional points of view. Maturation experiments (at fixed temperature) will also be performed in order to estimate the dependency in time.
Contacts
Romain AUGIER (romain.augier@univ-orleans.fr), Hugues Raimbourg (hugues.raimbourg@univ-orleans.fr)
Deadline to apply
April the 23rd, 2018